Abstract: In order to ensure the production without pollution in offshore gasfield,when there is no available study process and mode,based on shallow preservation conditions,bridged by injectivity index and constrained by formation fracture pressure,a study of produced water reinjection in gas field A was carried out,which includes shallow fracture system,reinjection zone selection and injection capacity analysis,and then the study feasibility was verified by numerical simulation,which provides a reference for produced water reinjection in offshore gas field.The results indicate the shallow strata form A gas field is relatively complete,with less faults development,from Santan formation to sea bottom,there was no fault development.The influence of produced water reinjection in gas field is small and there is no fault risk of overflow.